U.S. patent number 3,958,551 [Application Number 05/553,140] was granted by the patent office on 1976-05-25 for compound bow.
This patent grant is currently assigned to AMF Incorporated. Invention is credited to Frank W. Ketchum.
United States Patent |
3,958,551 |
Ketchum |
May 25, 1976 |
Compound bow
Abstract
Pairs of individually changeable cam wheels at the tips of a
compound bow for selective adjustment of the weight and draw length
of the bow. The wheels have halves having different size grooves,
said halves being interchangeable thus offering a full range of
different weight and draw length bows.
Inventors: |
Ketchum; Frank W.
(Jacksonville, TX) |
Assignee: |
AMF Incorporated (White Plains,
NY)
|
Family
ID: |
24208279 |
Appl.
No.: |
05/553,140 |
Filed: |
February 26, 1975 |
Current U.S.
Class: |
124/25.6;
124/90 |
Current CPC
Class: |
F41B
5/10 (20130101); F41B 5/105 (20130101) |
Current International
Class: |
F41B
5/10 (20060101); F41B 5/00 (20060101); F41B
005/00 () |
Field of
Search: |
;124/23R,24R,3R,3A,35A |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Pinkham; Richard C.
Assistant Examiner: Browne; William R.
Attorney, Agent or Firm: Price; George W. Lewis; Walter
Claims
I claim:
1. In a compound bow having a central handle, a pair of resilient
limbs, a bow string spanning the ends of said limbs, and a
mechanical advantage device at the ends of said limbs for said
string to increase the energy input into said bow and then reduce
the force required to hold said string at full draw, the
improvement of each of said devices comprising a rotatable wheel
assembly having two side by side wheels of unequal diameter which
are adapted to turn in unison about a common axis, each of said
wheels having a circumferential groove formed therein, the opposite
ends of the central stretch of said string being disposed in one of
said grooves, the end stretches of said string being disposed in
the other of said grooves, and means for adjusting the draw length
of said bow independent of the same energy input to said bow, said
means comprising replacement means to change just the size of the
grooves for the central stretch of said string.
2. In a compound bow as in claim 1, wherein said two side by side
wheels of said rotatable wheel assemblies are integral with each
other, and said replacement means comprises at least two other such
two wheel integral assemblies, the wheels of all said assemblies
having the grooves therein for said end stretches being of equal
diameter, and the other wheels of said two other wheel assemblies
having equal, but different diameters from the corresponding wheels
of the first two mentioned wheel assemblies to provide different
draw lengths for said bow independent of the same energy input
thereto.
3. In a compound bow as in claim 1, wherein said two side by side
wheels of said rotatable wheel assemblies are separably connected
to each other, said replacement means comprising at least two other
wheels for substitution for the wheels of said assemblies having
the grooves therein for said central stretch, and said last
mentioned wheels and said two other wheels having different
diameters to provide different draw lengths for said bow
independent of the same energy input thereto.
Description
This invention relates to a compound bow, and more particularly to
means for making independent selective adjustments in the weight
and draw length of the bow.
One type of compound bow is illustrated in Allen U.S. Pat. No.
3,486,495 (1969). In this bow, oval or circular eccentric grooved
wheels are provided at the bow tip ends. The bow string is strung
around the eccentric wheels. These eccentric wheels provide a
mechanical advantage to increase the amount of energy stored in the
bow before full draw, and then a let off in the amount of force
required to hold the string at full draw.
The wheels have a pair of grooves therein, one for the let off side
or central stretch of the bow string, and the other for the take up
side or end stretches of the string. Some adjustments can be made
to the bow by changing the size of the wheels, but this is limited.
This is because heretofore each time the wheel was changed both
grooves were changed. For example, to get an appreciable increase
in the draw length, a larger wheel was selected. However, a larger
wheel resulted in stressing the bow beyond its maximum rated
weight. Of course, reducing the size of the wheel to reduce the
draw length meant that the bow was being operated below its
capacity.
In the invention, each side of the wheel is adjusted independent of
the other side. Thus, for example, in order to increase the draw
length, just the central stretch groove or let off side of the
wheel is enlarged, but not the other groove or take up side of the
wheel. This means that with the increased draw length the bow
continues to operate at or near its maximum rated capacity.
The invention will be better understood by considering the
following detailed description taken in connection with the
accompanying two sheets of drawing in which:
FIG. 1 is a perspective view of a compound bow of the prior
art;
FIG. 2 is an enlarged perspective view of the wheel at the upperend
of FIG. 1;
FIGS. 3 and 4 are side elevation views of one form of the
invention;
FIGS. 5 and 6 are side elevation views of a second form of the
invention; and
FIGS. 7 and 8 are side elevation views of a third form of the
invention.
Referring now first to FIG. 1, the compound bow comprises a central
handle 10, a pair of resilient limbs 11, eccentric wheels 12, a
pair of idler pulleys 13, and a bow string 17 strung around the
wheels and pulley and anchored at its opposite ends to the opposite
ends of the handle.
Referring now also to FIG. 2, the wheels 12 are rotatably mounted
on eccentrics 14. The wheels 12 have a pair of grooves 15, 16
formed therein. The bow string 17 has a central stretch 17'.
Opposite ends of the central stretch 17' are disposed in grooves 15
for almost a full turn and then go in a radial hole 15' to an axial
hole 18. From the axial hole 18, end stretch 17" of the string 17
continues out through another radial hole 16' to the groove 16 for
about a quarter of a turn and then along the length of the bow to
the opposite idler pulley 13 and then to the adjacent end of the
handle 10. The central and end stretches 17' and 17" are shown as
being discontinuous, but they in effect are continuations of each
other and can in fact be actual continuations of each other
provided means is provided to prevent slippage of the string in the
grooves. In the design shown in FIG. 2, a not shown pin or the like
is driven into the axial bore 18 to pinch the adjacent ends of
string ends 17' and 17" to prevent them from slipping on the wheel
12. As heretofore stated, it has been the practice to make
adjustments in the draw length by changing the size of the wheel.
This resulted in more or less string or cable in the groove 15, but
the same was also true for groove 16. In other words, by merely
changing the size of the wheel it was not possible to make
selective adjustments in just the weight or draw length of the bow.
My invention shows how this can be readily accomplished, at low
cost, plus providing other advantages.
Referring now to FIGS. 3 and 4, in this form of the invention, a
replacement two-step integral wheel is provided in which the groove
16 is the same size as in FIG. 2, whereas the size of groove 15a is
reduced from that of 15 in FIG. 2, so that the draw length is
changed but without changing the weight of the bow.
In the form of the invention shown in FIGS. 5 and 6 another
two-step wheel is shown as in FIGS. 3 and 4; however, here the two
parts are separably joined together by means such as studs 19 so
that with such an arrangement of the parts a great plurality of
different sized wheel halves can be interchanged with each other to
readily selectively change the bow weight and/or draw length. The
holes 15", 16" and 18' in FIG. 5 correspond in purpose to the holes
15', 16' and 18 of FIGS. 2 and 3. In addition, however, the bearing
14 for the eccentric axis in FIG. 5 is formed just in the take up
or end stretch side of the wheel (that is, just the part having the
groove 16). This provides the advantage that, as compared to FIGS.
2 and 3, the entire wheel does not have to be unstrung and removed
from its pivotal mounting on the bow ends in order to adjust just
the draw length. By virtue of the studs 19 and slot 20, it is
necessary to change just the central stretch 17' and the part of
the let off or central stretch side of the wheel (that is, just the
part having the groove 15a) in order to change the draw length.
That is to say, the part of the wheel having the groove 16 and the
end stretches 17" do not have to be disassembled in order to change
just the draw length, and in changing the draw length the weight of
the bow is in no way affected.
It will be seen that by using the approach of FIGS. 5 and 6 the
invention makes it possible to economize on the number of parts
required to make a wide range of adjustments in the draw length
and/or weight of the bow. That is to say, by providing a set of
wheel halves having different size grooves 15a and another set of
wheel halves having different sizes grooves 16, which can be
interchanged, a full range of compound bows having different
weights and draw lengths is provided for at the time of manufacture
and also for the end user as well.
The embodiment of the invention illustrated in FIGS. 7 and 8 is
similar in principle to that of FIGS. 5 and 6, except that the
wheel part having the groove 15a is not on an eccentric axis. That
is to say, the axis 14 is an eccentric one for the part having the
groove 16, but a concentric one for the part having the groove 15a.
This is because both wheel halves do not have to be on an
eccentric, as shown in Allen U.S. Pat. No. 3,486,495, in order to
obtain a drop off in the amount of force required to hold the bow
at full draw. In order to achieve a drop off it is necessary for
only the wheel part having the groove 16 (that is, the take up or
end stretch side) to be rotatable about an eccentric axis.
* * * * *